The Animal Rescue League of Boston (ARL), one of the region’s largest animal welfare organizations, has received its largest ever donation as it pursues its fundraising goals to build out a new facility and expand its operational capacities.

The $2 million gift from longtime ARL supporters Arthur and Paula Rabe was announced by the organization on Nov. 13.

ARL is in the process of constructing a brand new three-story, 35,000 square-foot state-of-the-art building at its 10 Chandler St. location in the South End.

The project is set to cost $48 million and broke ground in June, according to ARL. With it, ARL aims to provide a veterinary hospital, an animal care and adoption center and a hub for pet owner supportive services in the center of Boston.

“Our Boston shelter is the heart and soul of the ARL, but it is outdated and no longer meets the standard of care that animals deserve and that we can provide,” said Dr. Edward Schettino, the president and CEO of ARL, in a statement.

“Our new flagship facility is a crucial investment in the future of animal welfare and ensures we can meet the growing demand for low-cost, high-quality veterinary care, temporary pet housing, and expert resources that pet owners rely on,” Schettino added.

Schettino said that ARL is “profoundly grateful” for the Rabe’s generous donation. The Chestnut Hill couple first connected with ARL in 2007 with the adoption of their cat, Jill. They later adopted a second cat named Paul from the organization.

ARL originally set up a fundraising campaign of $10 million, but after surpassing this goal, it has expanded its target to $12 million.

ARL said it is currently 96% to goal and is now asking for the public’s help to get the fundraising campaign across the finish line.

Any donation to ARL’s campaign will be matched up to $715,000 through a gift from the estate of benefactor Barbara Loke, the organization said.

The new building is also meant to address increased demand from pet owners who are being squeezed by the housing crisis, food insecurity and the high costs of veterinary care, ARL said.

At the same time, ARL aims to use its new expanded footprint for designated quarantine spaces for animals transported to Boston from out of state.

Dogs and cats brought across state lines into Massachusetts must quarantine for a minimum 48-hour window upon arrival under state law, which can create an initial upfront spacing issue for large intakes of animals all at once.

Dogs brought to Massachusetts from Louisiana by the Animal Rescue League of Boston

The organization frequently partners with the BISSELL Pet Foundation to relocate animals from higher need areas of the country, particularly the South, acting as a pressure release valve for local animal rescue organizations.

The group recently received six dogs from Louisiana at its Dedham campus, including four 4-month-old puppies.

Each year, ARL said that it helps more than 20,000 animals. The group is reliant upon the generosity of its supporters to fund its work as it receives no government funding.